The present invention relates to a fuel injection control apparatus of an internal combustion engine and a fuel injection method of an internal combustion engine.
Up to now, by carrying out a fuel control in which a desirable injection characteristic of a fuel injector can be obtained, a fuel injection control apparatus having a wide range linear characteristic area has been proposed. For example, Japanese patent application laid-open No. Hei 9-209803 discloses, in a fuel injection control apparatus constituted by including an operation condition detection means for defecting an engine operation condition, a fuel injection amount establishment means for establishing a fuel injection mount to the engine according to the detected engine operation condition, and a fuel injection control means for carrying out a fuel injection control according to the established fuel injection amount through a fuel injector. A fuel injection control apparatus for use in an internal combustion engine is characterized in that the fuel control apparatus is constituted including a correction amount establishment means for establishing a correction amount to have a desirable injection characteristic of the fuel injection amount from the fuel injector, and a fuel injection amount correction means for correcting the fuel injection mount is established by the fuel injection amount establishment means according to the established correction amount.
The above stated desirable injection characteristic is a relationship between a drive signal to the fuel injector and the fuel injection amount having the linear characteristic in which a substantially constant inclination extending over at substantially whole area.
In an engine such a lean burn engine and a cylinder-in injection gasoline engine, at a small area of the fuel injection amount, an actual fuel injection amount against a control value becomes small, namely there happens that a direction of a fuel pulse width disagrees with a direction of an increase area of the fuel amount. With the above stated reasons, an unstable use area exists in the small area of the fuel injection amount, there is a concern about inviting aggravation of the operability and the exhaust gas property. With these reasons, in the conventional example stated above, it has been proposed that the correction amount is determined to obtain that the relationship between the drive signal to the fuel injector and the fuel injection amount has the linear characteristic having a substantially constant inclination extending substantially over the whole area.
However, when the above stated linear characteristic control is carried out or not carried out, in the area where the fuel injection amount becomes further small, it is impossible to carry out the correspondence between the fuel injection amount and the fuel injection pulse width. This area is positioned as the use impossible area and the pulse width limitation is carried out.